In the internal combustion engine of a vehicle, an air-fuel mixture is made lean and the engine is operated, thereby reducing the generation of harmful exhaust gas components and improving fuel consumption.
If the air-fuel mixture is too lean, however, defective combustion occurs in the combustion chamber and uncombusted gas can flow into the exhaust system side and cause occurrence of a "flameout" (that is, combustion of fuel occurs in the exhaust system at a location outside of the combustion chamber). If a flameout occurs as mentioned above, damage to or deterioration in the function of the catalyst device or the like occurs. Therefore, a fuse sensor is attached on the downstream side of the catalyst device (i.e., catalytic converter) and when the temperature of the catalyst device rises to a set value or higher due to the flameout, then the fuse sensor detects such a temperature state, and such temperature state is displayed by a meter or a warning lamp on a panel, thereby informing the operator of the occurrence of the flameout.
Such a flameout detecting apparatus and a control apparatus for an internal combustion engine are disclosed in, for example, JP-A-55-137342 and JP-A-2-55859. According to the apparatus disclosed in JP-A-55-137342, by controlling an air-fuel ratio by detecting outputs corresponding to an exhaust pressure state from an exhaust pressure sensor and an engine rotational speed state, a limitative leaning process of the air-fuel mixture can be realized without causing a flameout. According to the apparatus disclosed in JP-A-2-55859, a flameout is detected by using a fluctuation amount at the time of rotation upon idling.
The apparatus disclosed in JP-A-55-137342 has disadvantages in that it is necessary to newly provide a special exhaust pressure sensor to detect a flameout and the costs increase and the construction becomes complicated.
In the apparatus disclosed in JP-A-2-55859, although a rotation fluctuation is used as a parameter for the flameout detection, in using such a parameter, there is a disadvantage in that the flameout detection cannot be discriminated in a high rotational speed range exceeding about 3,000 r.p.m. due to problems of vibration or the like.
Further, in a vehicle having a catalyst apparatus, there are disadvantages in that the temperature of the catalyst device abnormally rises during the flameout due to a delay in detection of the flameout, so that deterioration of the catalyst device occurs early and the durability of the catalyst device deteriorates and, in the worst case, the catalyst device is broken.
Further, there is a disadvantage in that a purification ratio of the exhaust gas from the internal combustion engine deteriorates due to deterioration of or damage to the catalyst device, and environmental pollution therefore increases.
In an attempt to eliminate the above disadvantages, it is an object of the present invention to provide an apparatus for detecting a flameout of an internal combustion engine comprising: a rotational speed sensor to detect the engine rotational speed of the internal combustion engine; an A/F sensor to detect the air-fuel ratio of the exhaust gas; an engine load sensor to detect the load state of the internal combustion engine; and control means for comparing an output signal from the A/F sensor and an output signal from the engine load sensor when the A/F sensor has generated a lean signal, for discriminating a flameout state, and for controlling so as to accommodate a response speed of the A/F sensor determined in accordance with the output signals of the rotational speed sensor and the engine load sensor, wherein a flameout is detected early to prevent a large quantity of uncombusted gas from being discharged into the atmosphere due to the flameout and for preventing deterioration of or damage to the catalyst device.
The invention comprises: a rotational speed sensor for detecting the rotational speed of the internal combustion engine and for generating an electric signal corresponding to the engine rotational speed; an A/F sensor for detecting the air-fuel ratio of the exhaust gas and for generating an electric signal corresponding to the air-fuel ratio; an engine load sensor for detecting the load state of the internal combustion engine and for generating an electric signal corresponding to the load state; and control means for comparing the output signal from the A/F sensor and the output signal from the engine load sensor when the A/F sensor has generated a lean signal, for discriminating a flameout state, and for controlling response speed of the A/F sensor in accordance with the output signals of the rotational speed sensor and the engine load sensor.
According to the construction of the invention, when the A/F sensor generates a lean signal, the control means respectively receive the output signals from the A/F sensor and the engine load sensor and compares the output signals to thereby discriminate a flameout state, the control means also controls so as to correct the response speed of the A/F sensor in accordance with the output signals from the rotational speed sensor and the engine load sensor and detects early the occurrence of the flameout and can execute a countermeasure to promptly prevent continuation of the flameout. Therefore, it can be prevented that a large quantity of uncombusted gas is discharged into the atmosphere. Deterioration of or damage to the catalyst device can also be prevented. The durability and useful life of the catalyst device is improved.